docs: def _earth_orientation(date):
      """Earth orientation parameters in degrees
      """
  
      ttt = date.change_scale('TT').julian_century
      # a_a = 0.12
      # a_c = 0.26
      # s_prime = -0.0015 * (a_c ** 2 / 1.2 + a_a ** 2) * ttt
      s_prime = - 0.000047 * ttt
  
      return date.eop.x / 3600., date.eop.y / 3600., s_prime / 3600